lib/Transforms/IPO/RaiseAllocations.cpp

   1 //===- RaiseAllocations.cpp - Convert @malloc & @free calls to insts ------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file defines the RaiseAllocations pass which convert malloc and free
  11 // calls to malloc and free instructions.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #define DEBUG_TYPE "raiseallocs"
  16 #include "llvm/Transforms/IPO.h"
  17 #include "llvm/Constants.h"
  18 #include "llvm/DerivedTypes.h"
  19 #include "llvm/LLVMContext.h"
  20 #include "llvm/Module.h"
  21 #include "llvm/Instructions.h"
  22 #include "llvm/Pass.h"
  23 #include "llvm/Support/CallSite.h"
  24 #include "llvm/Support/Compiler.h"
  25 #include "llvm/ADT/Statistic.h"
  26 #include <algorithm>
  27 using namespace llvm;
  28
  29 STATISTIC(NumRaised, "Number of allocations raised");
  30
  31 namespace {
  32   // RaiseAllocations - Turn @malloc and @free calls into the appropriate
  33   // instruction.
  34   //
  35   class VISIBILITY_HIDDEN RaiseAllocations : public ModulePass {
  36     Function *MallocFunc;   // Functions in the module we are processing
  37     Function *FreeFunc;     // Initialized by doPassInitializationVirt
  38   public:
  39     static char ID; // Pass identification, replacement for typeid
  40     RaiseAllocations()
  41       : ModulePass(&ID), MallocFunc(0), FreeFunc(0) {}
  42
  43     // doPassInitialization - For the raise allocations pass, this finds a
  44     // declaration for malloc and free if they exist.
  45     //
  46     void doInitialization(Module &M);
  47
  48     // run - This method does the actual work of converting instructions over.
  49     //
  50     bool runOnModule(Module &M);
  51   };
  52 }  // end anonymous namespace
  53
  54 char RaiseAllocations::ID = 0;
  55 static RegisterPass<RaiseAllocations>
  56 X("raiseallocs", "Raise allocations from calls to instructions");
  57
  58 // createRaiseAllocationsPass - The interface to this file...
  59 ModulePass *llvm::createRaiseAllocationsPass() {
  60   return new RaiseAllocations();
  61 }
  62
  63
  64 // If the module has a symbol table, they might be referring to the malloc and
  65 // free functions.  If this is the case, grab the method pointers that the
  66 // module is using.
  67 //
  68 // Lookup @malloc and @free in the symbol table, for later use.  If they don't
  69 // exist, or are not external, we do not worry about converting calls to that
  70 // function into the appropriate instruction.
  71 //
  72 void RaiseAllocations::doInitialization(Module &M) {
  73   // Get Malloc and free prototypes if they exist!
  74   MallocFunc = M.getFunction("malloc");
  75   if (MallocFunc) {
  76     const FunctionType* TyWeHave = MallocFunc->getFunctionType();
  77
  78     // Get the expected prototype for malloc
  79     const FunctionType *Malloc1Type =
  80       FunctionType::get(PointerType::getUnqual(Type::getInt8Ty(M.getContext())),
  81                       std::vector<const Type*>(1,
  82                                       Type::getInt64Ty(M.getContext())), false);
  83
  84     // Chck to see if we got the expected malloc
  85     if (TyWeHave != Malloc1Type) {
  86       // Check to see if the prototype is wrong, giving us i8*(i32) * malloc
  87       // This handles the common declaration of: 'void *malloc(unsigned);'
  88       const FunctionType *Malloc2Type =
  89         FunctionType::get(PointerType::getUnqual(
  90                           Type::getInt8Ty(M.getContext())),
  91                           std::vector<const Type*>(1,
  92                                       Type::getInt32Ty(M.getContext())), false);
  93       if (TyWeHave != Malloc2Type) {
  94         // Check to see if the prototype is missing, giving us
  95         // i8*(...) * malloc
  96         // This handles the common declaration of: 'void *malloc();'
  97         const FunctionType *Malloc3Type =
  98           FunctionType::get(PointerType::getUnqual(
  99                                     Type::getInt8Ty(M.getContext())),
 100                                     true);
 101         if (TyWeHave != Malloc3Type)
 102           // Give up
 103           MallocFunc = 0;
 104       }
 105     }
 106   }
 107
 108   FreeFunc = M.getFunction("free");
 109   if (FreeFunc) {
 110     const FunctionType* TyWeHave = FreeFunc->getFunctionType();
 111
 112     // Get the expected prototype for void free(i8*)
 113     const FunctionType *Free1Type =
 114       FunctionType::get(Type::getVoidTy(M.getContext()),
 115         std::vector<const Type*>(1, PointerType::getUnqual(
 116                                  Type::getInt8Ty(M.getContext()))),
 117                                  false);
 118
 119     if (TyWeHave != Free1Type) {
 120       // Check to see if the prototype was forgotten, giving us
 121       // void (...) * free
 122       // This handles the common forward declaration of: 'void free();'
 123       const FunctionType* Free2Type =
 124                     FunctionType::get(Type::getVoidTy(M.getContext()), true);
 125
 126       if (TyWeHave != Free2Type) {
 127         // One last try, check to see if we can find free as
 128         // int (...)* free.  This handles the case where NOTHING was declared.
 129         const FunctionType* Free3Type =
 130                     FunctionType::get(Type::getInt32Ty(M.getContext()), true);
 131
 132         if (TyWeHave != Free3Type) {
 133           // Give up.
 134           FreeFunc = 0;
 135         }
 136       }
 137     }
 138   }
 139
 140   // Don't mess with locally defined versions of these functions...
 141   if (MallocFunc && !MallocFunc->isDeclaration()) MallocFunc = 0;
 142   if (FreeFunc && !FreeFunc->isDeclaration())     FreeFunc = 0;
 143 }
 144
 145 // run - Transform calls into instructions...
 146 //
 147 bool RaiseAllocations::runOnModule(Module &M) {
 148   // Find the malloc/free prototypes...
 149   doInitialization(M);
 150
 151   bool Changed = false;
 152
 153   // First, process all of the malloc calls...
 154   if (MallocFunc) {
 155     std::vector<User*> Users(MallocFunc->use_begin(), MallocFunc->use_end());
 156     std::vector<Value*> EqPointers;   // Values equal to MallocFunc
 157     while (!Users.empty()) {
 158       User *U = Users.back();
 159       Users.pop_back();
 160
 161       if (Instruction *I = dyn_cast<Instruction>(U)) {
 162         CallSite CS = CallSite::get(I);
 163         if (CS.getInstruction() && !CS.arg_empty() &&
 164             (CS.getCalledFunction() == MallocFunc ||
 165              std::find(EqPointers.begin(), EqPointers.end(),
 166                        CS.getCalledValue()) != EqPointers.end())) {
 167
 168           Value *Source = *CS.arg_begin();
 169
 170           // If no prototype was provided for malloc, we may need to cast the
 171           // source size.
 172           if (Source->getType() != Type::getInt32Ty(M.getContext()))
 173             Source =
 174               CastInst::CreateIntegerCast(Source,
 175                                           Type::getInt32Ty(M.getContext()),
 176                                           false/*ZExt*/,
 177                                           "MallocAmtCast", I);
 178
 179           MallocInst *MI = new MallocInst(Type::getInt8Ty(M.getContext()),
 180                                           Source, "", I);
 181           MI->takeName(I);
 182           I->replaceAllUsesWith(MI);
 183
 184           // If the old instruction was an invoke, add an unconditional branch
 185           // before the invoke, which will become the new terminator.
 186           if (InvokeInst *II = dyn_cast<InvokeInst>(I))
 187             BranchInst::Create(II->getNormalDest(), I);
 188
 189           // Delete the old call site
 190           I->eraseFromParent();
 191           Changed = true;
 192           ++NumRaised;
 193         }
 194       } else if (GlobalValue *GV = dyn_cast<GlobalValue>(U)) {
 195         Users.insert(Users.end(), GV->use_begin(), GV->use_end());
 196         EqPointers.push_back(GV);
 197       } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
 198         if (CE->isCast()) {
 199           Users.insert(Users.end(), CE->use_begin(), CE->use_end());
 200           EqPointers.push_back(CE);
 201         }
 202       }
 203     }
 204   }
 205
 206   // Next, process all free calls...
 207   if (FreeFunc) {
 208     std::vector<User*> Users(FreeFunc->use_begin(), FreeFunc->use_end());
 209     std::vector<Value*> EqPointers;   // Values equal to FreeFunc
 210
 211     while (!Users.empty()) {
 212       User *U = Users.back();
 213       Users.pop_back();
 214
 215       if (Instruction *I = dyn_cast<Instruction>(U)) {
 216         if (isa<InvokeInst>(I))
 217           continue;
 218         CallSite CS = CallSite::get(I);
 219         if (CS.getInstruction() && !CS.arg_empty() &&
 220             (CS.getCalledFunction() == FreeFunc ||
 221              std::find(EqPointers.begin(), EqPointers.end(),
 222                        CS.getCalledValue()) != EqPointers.end())) {
 223
 224           // If no prototype was provided for free, we may need to cast the
 225           // source pointer.  This should be really uncommon, but it's necessary
 226           // just in case we are dealing with weird code like this:
 227           //   free((long)ptr);
 228           //
 229           Value *Source = *CS.arg_begin();
 230           if (!isa<PointerType>(Source->getType()))
 231             Source = new IntToPtrInst(Source,
 232                         PointerType::getUnqual(Type::getInt8Ty(M.getContext())),
 233                                       "FreePtrCast", I);
 234           new FreeInst(Source, I);
 235
 236           // If the old instruction was an invoke, add an unconditional branch
 237           // before the invoke, which will become the new terminator.
 238           if (InvokeInst *II = dyn_cast<InvokeInst>(I))
 239             BranchInst::Create(II->getNormalDest(), I);
 240
 241           // Delete the old call site
 242           if (I->getType() != Type::getVoidTy(M.getContext()))
 243             I->replaceAllUsesWith(UndefValue::get(I->getType()));
 244           I->eraseFromParent();
 245           Changed = true;
 246           ++NumRaised;
 247         }
 248       } else if (GlobalValue *GV = dyn_cast<GlobalValue>(U)) {
 249         Users.insert(Users.end(), GV->use_begin(), GV->use_end());
 250         EqPointers.push_back(GV);
 251       } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
 252         if (CE->isCast()) {
 253           Users.insert(Users.end(), CE->use_begin(), CE->use_end());
 254           EqPointers.push_back(CE);
 255         }
 256       }
 257     }
 258   }
 259
 260   return Changed;
 261 }